Three dimensional modeling weld solidification cracks in multipass welding

This paper utilizes element birth and death finite element technique to control the process of filling metal step by step during multipass welding process. The dynamic thermal distributions and strain evolutions are simulated in 10 mm SUS310 stainless steel in multipass welding after taking into consideration of the fluid flow in the weld pool, the latent heat, taking into account the effect of the deformation in weld pool, change of initial temperature and solidification shrinkage. At the same time, the driving forces to weld solidification cracks of each weld pass are obtained successfully according to simulated thermal cycle (temperature against time) and mechanical strain cycle (mechanical strain against time). The results show the patterns of distribution of the driving force are similar to those of surface fusion welding. The driving force of first weld pass is larger than following weld passes and the driving force decreases gradually in company with welding processing. Sequent welding processes affect the mechanical strain distributions of previous weld pass, of which the tensile mechanical strain changes to compressive strain. In addition, the driving forces are analyzed and weld solidification cracks are predicted during multipass welding. The predicted results agree well with the experiments. Therefore, the simulated results in this study provide the foundation for predicting weld solidification cracking in actual weldment.